Axial-bonding heterotrimers based on tetrapyrrolic rings: synthesis, characterization, and redox and photophysical properties.

We prepared two heterooligomeric arrays based on free base/metalloporphyrins at axial positions and a metalloid phthalocyanine as a basal scaffolding unit by using the axial-bonding capabilities as well as the known oxophilicity of dihydroxytin(IV) phthalocyanine. Both heterotrimers were completely characterized by elemental analysis, MALDI-TOF MS, and 1H NMR (one- and two-dimensional), UV/Vis, and fluorescence spectroscopy as well as cyclic voltammetry. The ground-state properties indicate that there is minimal pi-pi interaction between the macrocyclic units. The excited-state properties show that there is electronic energy transfer competing with photoinduced electron transfer from the singlet state of the axial porphyrin to the central metalloid phthalocyanine and a photoinduced electron transfer from the ground state of the axial porphyrin to the singlet state of the central metalloid phthalocyanine.